Automatic production line refers to a form of production organization in which product processes are realized by automated machine systems .
It is formed based on the further development of the continuous assembly line. Its characteristics are: the processing object is automatically transferred from one machine tool to another, and the machine tool automatically processes, loads, unloads, inspects, etc.; the worker’s task is only to adjust, supervise and manage the automatic line, and does not participate in direct operations ; all The machines and equipment all operate according to a unified rhythm, and the production process is highly continuous.
In the 1920s, with the development of industries such as automobiles, rolling bearings , small motors, and sewing machines, automatic lines began to appear in machinery manufacturing . The earliest automatic lines appeared in combination machine tools .
Before the 1920s, assembly lines and semi-automatic production lines first appeared in the automobile industry , and then developed into automatic lines. After World War II, the number of automatic lines increased dramatically in the machinery manufacturing industry in industrially developed countries .
Production line advantage
Products produced using automatic lines should have a large enough output; product design and technology should be advanced, stable, reliable, and remain basically unchanged for a long time. The use of automatic lines in mass and mass production can improve labor productivity , stabilize and improve product quality , improve labor conditions , reduce production area, reduce production costs , shorten production cycles , ensure production balance, and have significant economic benefits .
The automatic production line automatically operates or controls the process according to prescribed procedures or instructions without human intervention.
Its goal is to be “stable, accurate, and fast.” Automation technology is widely used in industry, agriculture, military, scientific research, transportation , commerce, medical care, services and homes. The use of automatic production lines can not only liberate people from heavy physical labor , partial mental labor , and harsh and dangerous working environments, but also expand human organ functions, greatly improve labor productivity, and enhance human beings’ ability to understand and transform the world .
In the machinery manufacturing industry, there are automatic lines for casting, forging, stamping, heat treatment, welding, cutting and mechanical assembly , as well as comprehensive automatic lines that include processes of different natures, such as blank manufacturing, processing, assembly, inspection and packaging.
Automatic cutting lines are the fastest growing and most widely used in the machinery manufacturing industry.
Mainly include: automatic lines of combined machine tools for processing boxes, shells, miscellaneous and other parts; automatic lines composed of general, specialized or special automatic machine tools for processing shafts, disc rings and other parts; rotating body processing Automatic line; rotor automatic line for processing simple small parts , etc.
1. First determine the cycle time: no matter what kind of product, it must be manufactured within the exact time it must be completed.
2. Unit process: Only for one product, the unit accessories are transported, assembled, processed and materials received.
3．Pilot: Make a device that can visually understand the takt time.
4. U-shaped production line: Arrange the equipment counterclockwise in the order of the project , and have one person responsible for the exit and entrance.
5. AB control: Only when the subsequent project has no products and the previous project has products, the project will be carried out.
6. Light signal: A device that communicates product abnormalities in the production line process.
7．Post-project collection: The products of the production line must meet the needs of post-project.
There are two types of connection methods for equipment in automatic lines: rigid connection and flexible connection.
In a rigidly connected automatic line, there is no material storage device between processes, and the processing and transmission of workpieces has a strict rhythm. When a piece of equipment fails and stops, it will cause the entire line to shut down. Therefore, there are high requirements for the working reliability of various equipment in rigidly connected automatic lines.
In the flexible connection automatic line, there is a storage device between each process (or section).
The rhythm of each process does not have to be strictly consistent. When a certain piece of equipment stops for a short time, the storage device can play a role in adjusting and balancing within a certain period of time. Therefore, it will not affect the normal operation of other equipment.
Comprehensive automatic lines, assembly automatic lines and long combined machine tool automatic lines often use flexible connections.
The workpiece transfer system of the automatic line generally includes a machine tool loading and unloading device , a transmission device and a storage device. In the rotating body processing automatic line, the conveying device includes a gravity conveying or forced conveying trough or channel, lifting, transposition and distribution devices, etc. Robots are sometimes used to perform certain functions of the conveyor. In the automatic line of combined machine tools, when the workpiece has a suitable conveying base surface , the direct conveying method is adopted. The conveying device includes various stepping conveying devices, indexing devices, turning devices, etc.
For irregular shapes and no suitable conveying base surface, The workpiece is usually mounted on the pallet fixture for positioning and transportation. In this case, a return device for the pallet fixture must be added.
The control system of the automatic line is mainly used to ensure that the machine tools, workpiece conveying systems, and auxiliary equipment in the line work normally according to the specified work cycle and interlocking requirements, and is equipped with fault detection devices and signaling devices.
In order to adapt to the debugging and normal operation requirements of the automatic line, the control system has three working states : adjustment, semi-automatic and automatic. In the adjustment state, it can be operated and adjusted manually to realize various actions of a single device; in the semi-automatic state, it can realize a single cycle of work of a single device ; in the automatic state, the automatic line can work continuously.
The control system has a “pre-stop” control function. When the automatic line needs to stop under normal working conditions, it can stop after completing a work cycle and all relevant moving parts of each machine tool return to their original positions. Other auxiliary equipment of the automatic line are set up according to process needs and automation level , such as automatic inspection device for cleaning machine workpieces , automatic tool changing device, automatic chip holding system and centralized cooling system , etc.
In order to improve the productivity of the automatic line , the working reliability of the automatic line must be ensured. The main factors affecting the reliability of the automatic line are the stability of the processing quality and the reliability of the equipment. The development direction of automatic lines is mainly to improve productivity and increase versatility and flexibility. In order to meet the needs of multi-variety production, an adjustable automatic line that can be adjusted quickly will be developed.
Automatic production lines save a lot of time and costs. In industrially developed cities, the maintenance of automatic production lines has become a hot spot. Automatic production line maintenance is mainly completed by operators and maintenance workers.
Two major methods for automatic production line maintenance:
Synchronous repair method: During production, if a fault is discovered, try not to repair it and adopt maintenance methods. The production line will continue to operate until holidays, and maintenance workers and operators will be centralized to repair all problems at the same time. The equipment will be in full production on Monday.
Partial repair method: If there is a major problem with the automatic production line, the repair time will be longer. Synchronous repair methods cannot be used. At this time, the holidays are used to gather maintenance workers and operators to repair a certain part. Wait until the next holiday to repair the other part. Ensure that the automatic production line does not stop production during working hours. In addition, try to use pre-repair methods in management. Install a timer in the equipment to record the working hours of the equipment, apply wear patterns to predict the wear of wearing parts, and replace wearing parts in advance to eliminate faults in advance. Ensure that the production line is at full capacity.
Maintenance of automatic production line:
Electric circuits, gas circuits, oil circuits and mechanical transmission parts (such as guide rails , etc.) must be inspected and cleaned before and after work;
The work process should be inspected, key parts should be randomly inspected, and abnormalities found should be recorded. Small problems should be dealt with before and after work (it does not take long), and accessories should be prepared for major problems;
Unify all line shutdowns for maintenance, make plans for wearing parts, and replace wearing parts in advance to nip problems in the bud.
The development of technologies such as digital control machine tools , industrial robots and electronic computers , as well as the application of group technology , will make automatic lines more flexible and enable the automation of multi-variety, small and medium-sized batch production. Multi-variety adjustable automatic lines reduce the economic batch size of automatic line production . Therefore, they are increasingly used in the machinery manufacturing industry and are developing towards more highly automated flexible manufacturing systems.